【作者】 刘云潺；

【导师】 黄纯；

【作者基本信息】 湖南大学 ， 电力电子与电力传动， 2007， 硕士

【摘要】 随着现代科学技术的发展,基于微处理器芯片的各种敏感性用电设备得到了广泛应用,对供电系统的电压质量提出了更高的要求,几个周期的供电中断或电压暂降都将影响这些设备正常工作,并造成巨大的危害,电压暂降与中断引起了人们的广泛关注,成为了最重要的电能质量问题。对于可有效解决电压暂降问题的动态电压恢复器(Dynamic Voltage Restorer, DVR)来说,实时、准确地检测出电压暂降的三大特征量(暂降幅值、持续时间和可能同时出现的相位跳变)是其工作的前提和关键问题之一。本文对有效值计算法、缺损电压法、单相电压变换平均值法、基波分量法、瞬时电压dq变换法、p-q-r理论法、小波分析算法等电压暂降常用检测算法进行了比较分析,对其中部分算法进行了仿真研究,总结了各种算法的优缺点及适用范围。本文给出了一种应用最新时频分析方法Hilbert-Huang变换(HHT)来分析电压暂降信号的方法。运用HHT变换从信号本身的尺度特征出发对信号进行分解的特点,对输入信号进行自适应的频带划分,可以从时频两方面同时对信号进行分析。对电压暂降信号进行EMD分解后求取其瞬时频率,可以得到电压暂降信号的发生和终止时刻;结合EMD分解和电压暂降信号的特点,给出了一种可以求取瞬时幅值和相角的计算方法。仿真结果表明HHT对电压暂降信号的检测取得了较好的检测效果。针对目前动态电压恢复器中常用的dq变换检测法只适用于三相对称扰动的问题,本文提出了一种可用于三相不平衡电压暂降的检测方法。该方法首先对信号进行双dq变换和无时延的单相dq变换,变换后的量经由形态低通滤波器滤波后,分别求得电压基波正序、负序和零序分量,继而推导计算出各相电压暂降的幅值、持续时间和相位跳变角。仿真结果验证了该方法的正确性,分析结果表明这种方法具有很好的实时性,适合DVR实时检测的需要。更多还原

【Abstract】 With the development of the modern science and technology, a lot of sensitive electric equipments based on MPU chip have been widely applied, and an interruption or voltage sag of several cycles will impact these equipments’ normal work and bring great damage. It has brought forth widely attentions and become the most important dynamic power quality problem. For the dynamic voltage restorer (DVR) that can effectively solve the question of voltage sag, the correct detection of the voltage sag characteristics (its magnitude, duration and phase-angle jump) is of great importance. This paper analysis the methods used in voltage sag detection, and finds that traditional methods for voltage sags characteristics detection are inadequate to give complete parameters.The latest time-frequency analyzing method, Hilbert-Huang transform(HHT), is applied to deal with the non-stationary voltage sag signals. HHT uses the scale of the signal to decompose and make self-adapting frequency band partition of the input signals. With the instantaneous frequency in this method, the present study also analyzes the signal in terms of both time and frequency, and thus gets the time at which the voltage signal occurs and terminates. Considering the voltage sag’s specialty, a method is provided to detect instantaneous amplitude and phase of voltage sag through HHT. Actually, the detecting effect is proved to be satisfactory. The voltage sag detection based on dq transform is usually used in DVR, but it is only applicable to symmetrical voltage sags. A new method to detect unbalanced voltage sags is presented in this paper, which can identify unbalanced voltage sags characteristics, such as magnitude, duration and phase-angle jump. The positive, negative and zero sequence can be gotten by using dq transform and morphological filter, and then voltage sags characteristics can be calculated. Simulation results prove that the proposed method is correct and it has better dynamic performance. It can meet the real time requirement to detect unbalanced voltage sags by DVR.更多还原